The 30-year-old former Poland international joins the Seagulls on a free transfer after having been released from Manchester United at the end of last season.
Kuszczak has signed a two-year contract with Brighton.
Brighton boss Gus Poyet told the club’s official website: “There were clubs in England and abroad interested in Tomasz, but it says a lot for the ambition of this club that he wanted to sign for Brighton.
“We had been tracking his progress for some time and he will provide real competition to both Casper Ankergren and Peter Brezovan for the goalkeeper’s jersey this coming season.
“That can only be a good thing for the team moving forward.”